Process for terpolymer polyblends having high gloss and ductility

ABSTRACT

The invention relates to a process for preparing terpolymer polyblends having high gloss and ductility in formed articles, wherein, rubber particles in an aqueous latex are reacted with an alkenyl aromatic, alkenyl nitrile and alkyl acrylate monomer formulation such that said rubber particles become grafted with at least a portion of said monomers while said monomers form a matrix terpolymer phase of said monomers followed by separating said matrix phase terpolymer and said grafted rubber particles from said latex as a terpolymer polyblend. The invention also relates to a composition of said process.

This is a division, of application Ser. No. 140,279, filed Apr. 14,1980, U.S. Pat. No. 4,308,355.

BACKGROUND OF THE INVENTION

It is known to graft diene rubber particles in an aqueous latex withalkenyl aromatic and alkenyl nitrile monomers to form conventional ABSpolyblends.

Such polyblends have used grafted rubber particles ranging from about0.01 to 0.25 microns to obtain high gloss in formed articles. Polyblendshaving these small particles have not had high levels of toughness orhigh elongation at fail. U.S. Pat. No. 3,509,237 has taught that thesedeficiencies can be overcome by adding up to 30% by weight of graftedlarge rubber particles, based on total grafted rubber content ofpolyblend. Said particles having a size of about 0.8 to 2.0 microns orlarger.

The use of small and large grafted rubber particles or broaddistributions of grafted rubber particles does improve toughness,however, gloss is lowered in proportion to the amounts of largeparticles used to gain toughness.

It has now been discovered that small diene rubber particles containedin an aqueous latex can be grafted with a particular monomer formulationof alkenyl aromatic, alkenyl nitrile and alkyl acrylate monomers, having1 to 20% by weight of said alkyl acrylate monomer, to form a terpolymerpolyblend having high gloss and toughness. Rubber particles in the rangeof about 0.01 to 0.50 microns, preferably about 0.1 to 0.25 microns, canbe used in the polyblend insuring high gloss in formed articles.

SUMMARY OF THE INVENTION

The invention relates to a process for preparing terpolymer polyblendshaving high gloss and toughness comprising the steps:

A. charging an aqueous latex having diene rubber particles dispersedtherein to a reaction zone,

B. mixing a monomer formulation of alkenyl aromatic, alkenyl nitrile andalkyl acrylate monomers with said latex, said alkyl acrylate monomerbeing present in an amount of about 1 to 20% by weight of said monomerformulation,

C. polymerizing said monomer in the presence of said latex such that,said rubber particles become grafted with at least a portion of saidmonomers while said monomers form a matrix terpolymer phase of saidmonomers,

D. separating said matrix terpolymer phase having said grafted rubberparticles dispersed therein from said latex forming said terpolymerpolyblend.

The invention relates to terpolymer polyblend composition comprising:

A. a matrix phase terpolymer of alkenyl aromatic, alkenyl nitrile andalkyl acrylate monomers,

B. a diene rubber phase grafted with said monomers as graft terpolymerand dispersed in said matrix phase as rubber particles having an averageparticle size of about 0.01 to 0.25 microns, said matrix and graftterpolymers having present about 1 to 20% by weight of said alkylacrylate monomer, and

C. optionally a copolymer of said alkenyl aromatic and alkenyl nitrilemonomers in an amount up to about 50% by weight of said matrix phase,said terpolymer polyblend having high gloss and ductility in formedarticles.

PREFERRED EMBODIMENTS

The monomer formulation comprises, at least principally, amonoalkenylaromatic monomer, a ethylenically unsaturated nitrile monomerand an alkyl acrylate monomer. The monoalkenylaromatic monomer comprisesat least one monomer of the formula: ##STR1## where Ar is selected fromthe group consisting of phenyl, halophenyl, alkylphenyl andalkylhalophenyl and mixtures thereof and X is selected from the groupconsisting of hydrogen and an alkyl radical of less than three carbonatoms.

Exemplary of the monomers that can be employed in the present processare styrene; alpha-alkyl monovinylidene monoaromatic compounds, e.g.,alpha-methylvinyl toluene, etc.; ring-substitute alkyl styrenes, e.g.,vinyl toluene, o-ethylstyrene, p-ethylstyrene, 2,4-dimethylstyrene,etc.; ring-substituted halostyrenes, e.g., o-chlorostyrene,p-chlorostyrene, o-bromostyrene, 2,4-dichlorostyrene, etc.; ring-alkyl,ring-halo-substituted styrenes, e.g., 2-chloro-4-methylstyrene,2,6-dichloro-4-methylstyrene, etc. If so desired, mixtures of suchmonovinylidene aromatic monomers may be employed.

Exemplary of the unsaturated alkenyl nitriles which may be used in theinterpolymers are acrylonitrile, methacrylonitrile, ethacrylonitrile andmixtures thereof.

Exemplary of the monomers which may be interpolymerized with themonoalkenylaromatic hydrocarbons and unsaturated nitriles are conjugated1,3 dienes, e.g., butadiene, isoprene, etc.; alpha-or beta-unsaturatedmonobasic acids and derivatives thereof, e.g., acrylic acid, methylacrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate,methacrylic acid and the corresponding esters thereof, acrylamide,methacrylamide; vinyl halides such as vinyl chloride, vinyl bromide,etc.; vinylidene chloride, vinylidene bromide, etc.; vinyl esters suchas vinyl acetate, vinyl propionate, etc.; dialkyl maleates or fumaratessuch as dimethyl maleate, diethyl maleate, dibutyl maleate, thecorresponding fumarates, etc. As is known in the art, the amount ofthese comonomers which may be included in the interpolymer will vary asthe result of various factors.

In addition, the monomer formulation at the time of polymerization mayinclude a preformed polymer or a partially polymerized material such asa partially polymerized monoalkenylaromatic hydrocarbon or interpolymerthereof.

The polymerizable monomer mixtures contain at least 20% by weight of themonoalkenylaromatic monomer and preferable at least 50% by weightthereof. They also contain at least 5% by weight of the unsaturatednitrile and preferably at least 10% by weight thereof. From thestandpoint of highly advantageous commercial practice, the monomerformulations contain 20 to 95% and preferably 60 to 85% by weight of thevinylidene aromatic hydrocarbon and 80 to 5% and preferably 40 to 15% byweight of the unsaturated nitrile.

Water soluble catalysts that can be used are the alkali metal peroxides,persulfates, perborates, peracetates and percarbonates, preferablypotassium persulfate and hydrogen peroxide. Such water soluble catalystsmay be activated with reducing agents to form conventional redoxsystems. Here, the preferred reducing agent can be sodium bisulfite orsalts of ferrous ions or reduced transitional metals such as cobalt,nickel and copper. A preferred redox system is made up of the ion coupleof Fe⁺⁺ /S₂ O₈ ⁻⁻ /HSO₃ ⁻.

The catalyst is generally included within the range of 0.001 to 3.0% byweight and preferably on the order of 0.005 to 1.0% by weight of thepolymerizable monomers depending primarily upon the monomer present.

As is well known, it is often desirable to incorporate molecular weightregulators such as mercaptans, halides and terpenes in relatively smallpercentages by weight, on the order of 0.001 to 1.0% by weight of thepolymerizable material. In addition, it may be desirable to includerelatively small amounts of antioxidants or stabilizers such as theconventional alkylated phenols. Alternatively, these may be added duringor after polymerization. The formulation may also contain otheradditives such as plasticizers, lubricants, colorants and non-reactivepreformed polymeric materials which are suitable or dispersible therein.

The Diene Rubber

The preferred rubbers are diene rubbers, including mixtures of dienerubbers, i.e., any rubbery polymer (a rubbery polymer having a secondorder transition temperature not higher than 0° centigrade, preferablynot higher than -20° centigrade, as determined by ASTM Test D-746-52T ofone or more of the conjugated, 1,3-dienes, e.g., butadiene, isoprene,2-chloro-1,3 butadiene, 1 chloro-1,3 butadiene, piperylene, etc. Suchrubbers include copolymers and block copolymers of conjugated 1,3-dieneswith up to an equal amount by weight of one or more copolymerizablemonoethylenically unsaturated monomers, such as monovinylidene aromatichydrocarbons (e.g. styrene; an aralkylstyrene, such as the o-, m- andp-methylstyrenes, 2,4-dimethylstyrene, the arethylstyrenes, p-tertbutylstyrene, etc.; an alphamethylstyrene, alphaethylstyrene,alpha-methyl-p-methyl styrene, etc.; vinyl naphthalene, etc.); arhalomonovinylidene aromatic hydrocarbons (e.g. the o-, m- andp-chlorostyrene, 2,4-dibromostyrene, 2-methyl-4-chlorostyrene, etc.);acrylonitrile; methacrylonitrile; alkyl acrylates (e.g. methyl acrylate,butyl acrylate, 2-ethylhexyl acrylate, etc.), the corresponding alkylmethacrylates; acrylamides (e.g. acrylamide, methacrylamide,N-butylacrylamide, etc.); unsaturated ketones (e.g. vinyl methyl ketone,methyl isopropenyl ketone, etc.); alpha-olefins (e.g., ethylene,propylene, etc.); pyridines; vinyl esters (e.g. vinyl acetate, vinylstearate, etc.); vinyl and vinylidene halides (e.g. the vinyl andvinylidene chlorides and vinylidene chlorides and bromides, etc.); andthe like.

A preferred group of rubbers are the stereospecific polybutadienerubbers formed by the polymerization of 1,3 butadiene. These rubbershave a cis-isomer content of about 30-98% and a trans-isomer content ofabout 70-2% and generally contain at least about 85% of polybutadieneformed by 1,4-addition with no more than about 15% by 1,2 addition.Mooney viscosities of the rubber (ML-4, 212° F.) can range from about 20to 70 with a second order transition temperature of from about -50° C.to -105° C. as determined by ASTM Test D-746-52T.

The diene rubber used in preparing the grafted diene rubber is acrosslinked diene rubber of the type described above. The stereospecificpolybutadiene rubbers are the most preferred for optimum physicalproperties of the polyblend.

Another preferred group of rubbers are those consisting essentially of75 to 100% by weight of butadiene and/or isoprene and up to 25% byweight of a monomer selected from the group consisting of monovinylidenearomatic hydrocarbons (e.g. styrene) and unsaturated nitriles (e.g.,acrylonitrile), or mixtures thereof. Particularly advantageoussubstrates are butadiene homopolymer or an interpolymer of 90 to 95% byweight butadiene and 5 to 10% by weight of acrylonitrile or styrene. Thediene rubber may contain up to about 2% of a crosslinking agent based onthe weight of the rubber monomer or monomers. The crosslinking agent canbe of the agents conventionally employed for crosslinking diene rubbers,e.g., divinylbenzene, diallyl maleate, diallyl fumarate, diallyladipate, allyl acrylate, allyl methacrylate, diacrylates anddimethacrylates of polyhydric alcohols, e.g., ethylene glycoldimethacrylate, etc.

EMULSION POLYMERIZATION PROCESS

In the emulsion polymerization grafting process, the monomers and rubbersubstrate are emulsified in water by use of suitable emulsifying agents,such as fatty acid soaps, alkali metal or ammonium soaps of highmolecular weight, alkali or alkaryl sulfates and sulfonates, mineralacid salts of long chain aliphatic amines, etc. Emulsifying agents whichhave proven particularly advantageous are ammonium oleate, sodiumpalmitate, sodium stearate and other sodium soaps. Generally, theemulsifying agent is provided in amounts of from about 0.1 to 15 partsby weight per 100 parts by weight of the monomers and water is providedin an amount of from about 1 to 4 parts per part of monomers and even inlarger ratios where greater dilution is desirable, all as those skilledin the art appreciate.

If desired, an aqueous latex formed in the emulsion polymerization ofthe rubber substrate may provide the aqueous solution onto which themonomers are grafted, with or without the addition of furtheremulsifying agents, water and the like.

Typical emulsion polymerization conditions involve temperatures in therange of from about 20° to 100° C. with agitation and preferably aninert atmosphere. Pressures of from about 1 to 100 pounds per squareinch may be employed and monomers and/or additional catalysts may beadded incrementally or continuously over a portion of the reactioncycle. Polymerization is preferably continued until substantially all,that is more than 90%, of the monomers have polymerized. The remainingmonomers and other volatile components are then distilled away from thelatex, preferable, which is then ready for further treatment.

Particle size of the emulsion latex graft particles may be varied byseeding, emulsifying agent concentration, agitation, rubber sizevariation through agglomeration prior to grafting, coagulationtechniques, etc. Preferred agglomeration procedures are provided byDalton's U.S. Pat. Nos. 3,558,541 and 3,551,370.

The particle size of the rubber has an effect upon the optimum graftinglevel for a graft copolymer. For example, a given weight percentage ofsmaller size rubber particles will provide considerably higher surfacearea for grafting than the equivalent weight of a larger size rubberparticle. Accordingly, the density of grafting can be varied dependingupon the size of the rubber particle. Generally, smaller graft polymerparticles will tolerate a higher superstrate/substrate ratio than largersize particles.

The particle size of the emulsion rubber graft copolymer has asignificant effect upon the gloss and physical properties of the productproduced by the processes of this invention. Typically, the particlesize of the graft copolymers used in the practice of the presentinvention may be varied from as little as about 0.01 microns to as largeas about 1.0 microns and preferably from about 0.05 to 0.80 micronsdepending upon the ultimate properties desired for a given product. Amost preferred rubber graft copolymer for use in the practice of thisinvention are graft copolymers having a weight average particle size offrom about 0.2 to 0.7 microns for the grafted rubber.

For emulsion polymerization processes, the rubber desirably has asignificant degree of crosslinking. With respect to the graftcopolymers, at least some degree of crosslinking is inherent during thegraft polymerization process and this desirably may be augmented throughthe addition of crosslinking agents or control of the polymerizationconditions.

Such emulsion grafted rubber particles can exist in particle sizedistributions known as bimodal particle size distributions, i.e., 50 to95% by weight of the particles have an average particle size of about0.05 to 0.40 microns and 5 to 50% of the particles have an averageparticle size of about 0.50 to 5.0 microns or larger.

The dispersed rubber phase increases the toughness of the new typepolymeric polyblend as measured by its Izod impact strength by Test ASTMD-256-56. It has been found that the impact strength of polyblendsincrease with the weight percent rubber dispersed in the polyblend asused in the present invention. The impact strength is also determined bythe size of the dispersed rubber particles, with the larger particlesproviding higher impact strength measured as a weight average particlesize diameter with a photosedimentometer by the published procedure ofGraves, M. J. et al., "Size Analysis of Subsieve Powders Using aCentrifugal Photosedimentometer," British Chemical Engineering 9:742-744(1964). A Model 3000 Particle Size Analyzer from Martin Sweets Co., 3131West Market St., Louisville, Ky. was used.

The product of the emulsion grafting process is the diene rubberparticles grafted with a portion of the monomers charged to the rubberlatex. In addition, the monomers form a terpolymer of said monomers as amatrix phase. The grafted monomers form a superstrate on the dienerubber particles as a substrate when the monomers are grafted with watersoluble catalysts.

Although the amount of polymeric superstrate grafted onto the rubbersubstrate may vary from as little as 10.0 parts by weight to 100.0 partsof substrate to as much as 250.0 per 100.0 parts and even higher, thepreferred graft copolymers will generally have a superstrate tosubstrate ratio of about 20 to 200:100 and most desirably about 30 to150:100. With graft ratios about 30 to 150:100, a highly desirabledegree of improvement in various properties generally is obtained.

Such surface or superstrate grafting causes the rubber particles todisperse readily in the matrix phase terpolymers when melt colloidedduring extrusion. In addition, the superstrate provides a compatibleinterface with the matrix phase to increase toughness or impactstrength. As taught supra the larger the amount of the rubber moiety ina polyblend the tougher the polyblend with ABS polyblends containing 2to 50% of said rubber moiety depending on toughness desired.

The aqueous latex charged in step (A) contains about 20 to 60% ofemulsified diene rubber particles have a rubber particle size of about0.01 to 0.5 microns. The matrix polymer phase formed duringpolymerization has a molecular weight of about 50,000 to 500,000. Thediene rubber particles after grafting and the matrix polymer formed canbe separated from the aqueous emulsion by coagulation with inorganicsalts such as MgSO₄, Al₂ (SO₄)₃ or acids such as acetic, hydrochloric orsulfuric used in amounts sufficient to stoichometrically neutralize theemulsify agents and cause coagulation. The grafted rubber particles andthe matrix polymer particles will form a coagulated crumb which separatefrom the aqueous phase of the latex and can be easily removed byfiltration, decanting or centrifuging followed by washing and drying. Asdisclosed, the matrix polymer phase formed during emulsionpolymerization cocoagulates with the rubber particles as part of thecoagulate forming an intimate mixture as an ABS polyblend of graftedrubber particles and matrix polymer particles. The melt extrusion ofsuch blends can further colloidally disperse the grafted rubberparticles in the matrix phase polymer as an ABS polyblend.

Another suitable method for separating said grafted rubber particles andsaid matrix phase from said latex is to mix additional monomerformulation into said latex after grafting in amounts sufficient toextract said grafted rubber particles and said matrix polymer particlesinto said additional monomer formulation as a liquid monomer phase andremoving said liquid monomer phase from the aqueous phase of said latexby decanting or centrifugation.

The ratio of the additional monomer used for extraction to the weight ofgrafted rubber particles and matrix phase polymer in the latex can beabout 2 to 1 to 5 to 1 by weight. The higher the amount of monomers usedthe less viscous is the liquid monomer phase formed and the more readilyit separates from the aqueous phase of the latex. Improved dewatering ofthe liquid monomer phase can be carried out by adding inorganic salts oracids to the latex to deemulsify the grafted rubber particles and matrixphase particles so that water is not occluded with the particles asextracted into the monomer phase. Said liquid monomer phase can be masspolymerized thermally or with said monomer-soluble catalysts attemperatures of 100° to 180° C. to completion or to conversions of 50 to90% followed by conventional devolatilization of the residual monomersproviding the new polyblend with additional matrix phase polymers. Suchmass polymerization can be carried out in stirred reactors, in plug flowtowers or tubular reactors. U.S. Pat. No. 3,751,010 discloses a stirredhorizontal, evaporatively cooled reactor which is suitable for the masspolymerization of said liquid monomer phase to form new polyblends.

ALKYL ACRYLATE MONOMERS

The alkyl acrylate monomers are those selected from the alkyl groupconsisting of C₁ -C₁₂ alkyl acrylates, e.g., methyl, ethyl, propyl,butyl, pentyl, hexyl, ethyl hexyl, heptyl, octyl, nonyl, decyl, dodecyl.

The preferred alkyl acrylate monomers are C₄ -C₁₀ alkyl esters ofacrylic acid. The alkyl acrylates are present in said monomerformulation in amounts of about 1 to 20% by weight based on said monomerformulation.

It has been discovered that the toughness of polyblends having smallrubber particles in the range of about 0.01 to 0.25 microns can beincreased by incorporation of alkyl acrylates in the monomer formulationused to graft the rubber and prepare the matrix phase polymer. Here, theelongation to fail can be increased as much as 300% and the multiaxialimpact strength by as much as 200%.

The technical advance is one of being able to increase the toughness ofsuch polyblends yet maintain very high gloss through the small rubberparticles. The present invention allows the use of small rubberparticles for gloss without incorporating large particles for toughnesswith loss of gloss.

The following examples are illustrative of the present process and arenot meant to limit the scope or spirit of the invention.

EXAMPLE 1

To a 250.0 parts of a latex of butadiene/acrylonitrile copolymer (93:7)containing 50.0 percent solids and with a gel content of about 75%approximately 1.0 part of rubber reserve soap as an emulsifier wereadded 70.0 parts water, 1.0 part rubber reserve soap and 1.0 partpotassium persulfate.

This emulsion was heated to 65° centigrade with stirring and then therewere added thereto over a period of about six hours 140.0 parts styrene,60.0 parts acrylonitrile and 3.0 parts of terpinolene. The emulsion washeld at temperature for one hour thereafter with stirring, cooled,coagulated by the addition of magnesium sulfate and the coagulant wasthen washed and dried. The resulting graft copolymer has a superstrateto substrate ratio of about 0.9:1.0 and a rubber particle size of about0.25 micron.

EXAMPLES 2-8

Example 1 was repeated adding butyl acrylate to the monomer formulationsuch that the graft polyblend had the desired designated weight percentof the butyl acrylate desired as shown in Table I. The graft polyblendsformed had about 38% rubber and were diluted to 22% rubber for testpurposes using styrene-acrylonitrile copolymer (70/30). The resultingblend was extruded into 30 mil sheet.

                  TABLE I                                                         ______________________________________                                                                               Multiaxial                                   Wgt. %   Type of  Elongation                                                                            Failure                                                                              Impact                                 Ex.   Acrylate Acrylate at Fail %                                                                             Mode   Strength                               ______________________________________                                        1     0        --       11      Brittle                                                                              15                                     2     4.5      Butyl    28      Ductile                                                                              17                                     3     14.5     Butyl    34      Ductile                                                                              28                                     4     21.0     Butyl    42      Ductile                                                                              38                                     5     5.0      Octyl    31      Ductile                                                                              25                                     6     10.0     Octyl    43      Ductile                                                                              43                                     7     5.0      Decyl    25      Ductile                                                                              21                                     8     10.0     Decyl    36      Ductile                                                                              34                                     ______________________________________                                    

It is evident from these data, that the optimum properties are obtainedwith the octyl acrylate, however, the range of properties using C₄ toC₁₀ alkyl esters of acrylic acid provide superior toughness.

What is claimed is:
 1. A process for preparing terpolymer polyblendshaving high gloss and toughness comprising the steps:A. charging anaqueous latex having polybutadiene rubber particles dispersed therein toa reaction zone, B. mixing a monomer formulation of alkenyl aromatic,alkenyl nitrile and alkyl acrylate monomers with said latex, said alkylacrylate monomer being present in an amount of about 1 to 20% by weightof said monomer formulation, C. polymerizing by emulsifying on watersaid monomers in the presence of said latex such that, said rubberparticles become grafted with at least a portion of said monomers whilesaid monomers form a matrix terpolymer phase of said monomers, D.separating said matrix terpolymer phase having said grafted rubberparticles dispersed therein from said latex forming said terpolymerpolyblend, wherein said polymerization in step (C) is carried out at 20°to 100° C., at 0.7 to 7 atms. of pressure with water soluble catalyst,said polybutadiene rubber particles having an average particle size ofabout 0.1 to 0.7 microns.
 2. A process of claim 1 wherein said alkenylaromatic monomer comprises at least one monomer of the formula: ##STR2##where Ar is selected from the group consisting of phenyl, halophenyl,alkyl phenyl and alkylhalophenyl and mixtures thereof and X is selectedfrom the group consisting of hydrogen and an alkyl radical of less thanthree carbon atoms.
 3. A process of claim 1 wherein said alkenyl nitrilemonomer is acrylonitrile, metha-acrylonitrile, ethylacrylonitrile ormixtures thereof.
 4. A process of claim 1 wherein said separation ofstep (D) is carried out by the coagulation of said aqueous latexfollowed by filtering, washing and drying said polyblend of said grafteddiene rubber and said matrix polymer phases.
 5. A process of claim 1wherein said diene rubber moiety is present in said polyblend in anamount of about 2 to 50% by weight based on said polyblend.
 6. A processof claim 1 wherein said latex has present said diene rubber particles inan amount of about 20 to 60% by weight based on said latex.
 7. A processof claim 1 wherein the weight ratio of alkenyl aromatic to alkenylnitrile monomers in said monomer formulation is about 85:15 to 60:40. 8.A process of claim 1 wherein said alkyl acrylate monomer is selectedfrom the group consisting of C₁ -C₁₂ alkyl acrylates.
 9. A process ofclaim 1 wherein said alkyl acrylate is butyl acrylate.
 10. A process ofclaim 1 wherein said water soluble catalysts are selected from the groupconsisting of alkali metal percarbonates, persulfates, perborates,peracetates and hydrogen peroxide or mixtures thereof.
 11. A process ofclaim 1 wherein said water soluble catalysts are activated as a redoxsystem.
 12. A process of claim 1 wherein said separation of step (D) iscarried out by the coagulation of said aqueous latex followed byfiltering, washing and drying said polyblend of said grafted dienerubber and said matrix polymer phases.
 13. A process for polymerizingterpolymer polyblends having the steps:A. charging an aqueous latexhaving polybutadiene rubber particles dispersed therein to a mixingzone, B. mixing a monomer formulation consisting essentially of styrene,acrylonitrile and alkyl acrylate monomers in said latex, said acrylatemonomer having present in an amount of 1 to 20% by weight of saidmonomer formulation, C. polymerizing by emulsifying on water saidmonomers in the presence of said latex such that said diene rubberparticles become grafted with at least a portion of said monomers whilesaid monomers form a matrix polymer phase of said polymers, D.separating said grafted rubber particles and said matrix polymer phasefrom said latex as a terpolymer polyblend, said grafted rubber particleshaving an average particle size of about 0.2 to 0.7 microns, saidpolymerization in step (C) is carried out at 20° to 100° C., at 0.7 to 7atms. of pressure with water soluble catalyst.